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United States Patent |
5,324,216
|
Toyohara
,   et al.
|
June 28, 1994
|
Jet pump system for a water jet propelled boat
Abstract
A jet pump system for a water jet propelled boat is disclosed that provides
for the adjustment of the area of the water intake opening or the water
entry angle as a function of the speed of the boat. During low speed
operation, the water inlet opening is adjusted to a maximum area, or the
water entry angle is adjusted to a maximum angle to enable sufficient
water to enter the water duct and permit efficient impeller operation. As
the boat speed increases beyond a predetermined speed, the water inlet
area is reduced, or the water inlet angle is reduced to prevent excess
water from entering the water duct, thereby reducing the drag on the boat.
Inventors:
|
Toyohara; Makoto (Hamamatsu, JP);
Tasaki; Hiroshi (Hamamatsu, JP)
|
Assignee:
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Sanshin Kogyo Kabushiki Kaisha (Hamamatsu, JP)
|
Appl. No.:
|
886937 |
Filed:
|
May 22, 1992 |
Foreign Application Priority Data
Current U.S. Class: |
440/47; 440/46 |
Intern'l Class: |
B63H 011/103 |
Field of Search: |
114/275,276,277
440/38,46,47
60/221,222
|
References Cited
U.S. Patent Documents
3456611 | Jul., 1969 | Johnson | 114/275.
|
3809492 | May., 1974 | Takaeda et al. | 440/46.
|
3910216 | Oct., 1975 | Shultz | 114/275.
|
3942463 | Mar., 1976 | Johnson et al. | 440/47.
|
4373919 | Feb., 1984 | Strangeland | 440/47.
|
4449944 | May., 1984 | Baker et al. | 440/47.
|
4531920 | Jul., 1985 | Stricker | 440/47.
|
4775341 | Oct., 1988 | Tyler et al. | 440/38.
|
Foreign Patent Documents |
263893 | Nov., 1986 | JP | 114/270.
|
1-145598 | Oct., 1989 | JP.
| |
3213496 | Sep., 1991 | JP | 440/47.
|
Primary Examiner: Huppert; Michael S.
Assistant Examiner: Brahan; Thomas J.
Attorney, Agent or Firm: Bacon & Thomas
Claims
We claim:
1. A jet pump system for a water jet propelled boat having a bottom and a
driving impeller rotatable in a water duct, comprising:
a) a water inlet duct communicating with the water duct so as to direct
water into the water duct, the water inlet duct having an inlet portion
defining at least one water intake opening;
b) adjustment means comprising a slide valve member operatively associated
with the water inlet duct so as to be slidably movable across the at least
one water intake opening so as to vary the area of the at least one water
intake opening in relation to the speed of the boat;
c) actuating means operatively connected to the slide valve member so as to
slide the slide valve member across the at least one water intake opening;
and
d) boat speed sensing means operatively connected to the actuating means
such that the slide valve member automatically decreases the area of the
at least one water intake as the speed of the boat increases beyond a
predetermined speed, wherein the boat speed sensing means comprises: (i) a
constricted flow section defined by the water inlet duct downstream of the
driving impeller; and (ii) a pressure hose opening into the constricted
flow section and operatively connected to the actuating means.
2. The jet pump system of claim 1 wherein the actuating means comprises an
actuating cylinder connected to the slide valve member and operatively
associated with the pressure hose such that boat speed above a
predetermined speed increases pressure in the constricted flow section,
which increased pressure causes the actuating cylinder to move the slide
valve member so as to reduce the area of the water intake opening.
3. The jet pump system of claim 2 wherein the actuating cylinder further
comprises a piston rod connected to the slide valve member and biasing
means biasing the slide valve member toward a position in which the area
of the water intake opening is at a maximum.
4. The jet pump system of claim 1 wherein the actuating means causes the
slide valve member to decrease the area of the at least one water intake
opening when the boat speed increases beyond a predetermined speed and to
increase the area of the at least one water intake opening when the boat
speed decreases below the predetermined speed.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a jet pump system for a water jet
propelled boat, more particularly such a system which controls the water
inlet as a function of boat speed.
Water jet propelled boats are well-known in the art and typically have a
motor driven impeller located in a water duct. Water, which is drawn into
the duct through a water intake opening in the bottom of the boat, is
accelerated by the impeller and is ejected through a steering nozzle
located in the stern of the boat. The reaction force of the water through
the nozzle propels the boat forward. The nozzle may be pivoted about a
generally vertical axis to steer the boat.
In the past, the water intake opening and the water duct have been made of
a rigid material, such as metal or fiberglass reinforced plastic (FRP) and
have been fixed in area. The fixed areas of the water intake opening and
the water duct have inherently resulted in a compromise in boat
performance. Depending upon the speed of the boat, different dynamic
pressures act on the water intake. The dynamic pressures are higher when
the boat is running at high speed and are lower when it is running at low
speeds. Therefore, in boats where high speed operating characteristics are
important, the water intake opening has been designed to have a relatively
small area to prevent unneeded water from being introduced into the water
duct which thereby increases drag on the boat. The smaller water intake
opening allows the boat to achieve optimum speeds.
With the high speed boats, however, their low speed acceleration
characteristics are poor. Because of the small area of the water intake
opening, which facilitates high speed operation, almost no dynamic
pressure is acting upon it during low speed operations. Even if the
impeller can draw some water into the water duct, there is increased
resistance at the water intake opening, due to its small area, which
prevents sufficient water from being drawn into the water duct to achieve
good acceleration characteristics.
In boats intended for low speed operation, the water intake opening is
designed with a large area to enable sufficient water to be drawn into the
opening with little dynamic pressure at low speeds. With this type of boat
propulsion, however, the dynamic pressure increases when cruising at high
speeds since more water is drawn in than is needed by the pump. This
increases pump resistance and lowers the maximum speed.
Thus, the known water jet propelled boats with fixed water intake openings
could not achieve both high and low speed optimum operations.
The adjustment of the water intake angle also contributes to the enhanced
operational characteristics. When cruising at low speeds, the relative
speed between the boat and the water is low and, in a direction parallel
to the water intake opening (parallel to the bottom of the boat) there is
a low water inflow speed. Therefore, a higher water entry angle at low
speeds allows water to flow into the duct without significant resistance.
This results in good low speed acceleration characteristics.
When operating at high speeds, however, because of the greater water entry
speed in a direction parallel to the water intake opening, water becomes
detached from the leading edge of the water inlet, thereby increasing the
duct resistance, lowering intake efficiency and lowering maximum speed. If
the water entry angle is reduced at the water intake opening, this high
speed shear is prevented, thereby enhancing high speed operation. However,
this increases the intake resistance at the water intake opening during
low speed operation and causes poor acceleration characteristics.
SUMMARY OF THE INVENTION
A jet pump system for a water jet propelled boat is disclosed that provides
for the adjustment of the area of the water intake opening or the water
entry angle as a function of the speed of the boat. During low speed
operation, the water inlet opening is adjusted to a maximum area, or the
water entry angle is adjusted to a maximum angle to enable sufficient
water to enter the water duct and permit efficient impeller operation. As
the boat speed increases, the water inlet area is reduced, or the water
inlet angle is reduced to prevent excess water from entering the water
duct, thereby reducing the drag on the boat.
The present invention provides a mechanism for varying the water entry
angle into the duct, more particularly the angle between a wall of the
water inlet duct and the bottom of the boat to allow optimum performance
in both high and low speed operating modes.
By decreasing the area of the water intake opening as the boat speed
increases, the requisite amount of water can be taken into the water duct
without excess water resistance. The area of the water intake opening is
at a maximum when the boat operates at low speeds to enable a sufficient
amount of water to be taken into the water duct without negative pressure
developing. During low speed operation, the water entry angle is also at a
maximum so that if the boat is accelerated, sufficient water can be drawn
into the duct without undue resistance. The water entry angle of the duct
is reduced during high speed operation so as to prevent the development of
shear in the area of the intake opening.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a bottom view of a boat with a first embodiment of the jet pump
system according to the present invention.
FIG. 2 is a cross-sectional view taken along line II--II in FIG. 1.
FIG. 3 is a bottom view of a boat with a second embodiment of the jet pump
system according to the present invention.
FIG. 4 is a cross-sectional view taken along line IV--IV in FIG. 3.
FIG. 5 is a schematic diagram of the control system for the second
embodiment of the jet pump system according to the present invention.
FIG. 6 is a flow chart for the control system schematically illustrated in
FIG. 5.
FIG. 7 is a partial, cross-sectional view of a third embodiment of the jet
pump system according to the present invention.
FIG. 8 is an enlarged partial, cross-sectional view of the jet pump system
shown in FIG. 7 with the flexible wall oriented in a first position.
FIG. 9 is an enlarged cross-sectional view similar to FIG. 8, showing the
flexible wall in a second position.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The first embodiment of the present invention will be described in
reference to FIGS. 1 and 2. A boat hull 10 has boat bottom 12 which
defines a generally rectangular water intake opening 20. A pump unit 30
comprises a steering nozzle 32 which may be attached so as to pivot around
pivot shaft 34 to enable the steering nozzle 32 to move left or right so
as to steer the boat. Drive shaft 36 is driven by an engine (not shown) so
as to rotate impeller 38, which is affixed to the rear portion of the
drive shaft 36. A water duct 40 communicates with a water intake opening
20 and the steering nozzle 32. The water duct 40 comprises a forward
section 42, a midsection 44 having a generally horizontal orientation and
surrounding the impeller 38, and a constricted, downstream portion 46
which is connected to the steering nozzle 32.
The rotation of impeller 38 within the water duct 40 creates a water jet
flow. This jet flow uses water drawn in through the water intake opening
20, which then passes through forward section 42 of the water duct 40 into
the mid section 44. The water is accelerated through the constricted
portion 46 by the impeller 38 and is ejected through nozzle 32. The
reaction from the jet stream drives the boat forward.
A screen 22 may be attached over the water intake opening and may comprise
a plurality of rod-shaped elements running fore and aft in the direction
of travel of the boat. Screen 22 prevents foreign matter from entering the
duct and contacting the rotating impeller. A slide valve 50 is located in
the rear portion of water intake opening 20 and is mounted so as to slide
freely in valve groove 52. As shown in FIG. 1, slide valve 50 may comprise
individual valve elements located between the rod members of the screen 22
and which are connected by rod 50b. The slide valve 50 is configured such
that it slides fore and aft in the spaces defined by the water intake
opening and the screen 22. The leading edge 50a of the slide valve 50,
when viewed from the top or bottom, forms a generally "U" shape. Its
configuration when viewed from the side, as seen in FIG. 2, is such that
its lower edge protrudes beyond an upper edge so that it conforms to the
shape of the inner surface of forward section 42 of water duct 40.
Slide valve 50 is operatively linked to piston rod 56 which is slidably
connected to a piston within cylinder 54. Cylinder 54 is attached to the
boat structure outside of the water duct 40. The interior of cylinder 54
communicates with the constricted area 46 of the water duct 40 by pressure
hose 57 and opening 59. A compressed spring (not shown) is located within
cylinder 54 and exerts a force against the piston rod 56 so as to bias the
slide valve 50 to a normally open position.
During low speed operation, the rotational speed of impeller 38 is
relatively low, thereby creating a relatively weak jet stream in the mid
section 44 of the water duct 40. This jet stream is accelerated in the
constricted area 46, but since the jet flow is weak, the pressure does not
rise to a great extent in the constricted area 46.
The pressure within the constricted area 46 is transmitted to the inside of
cylinder 54 via the pressure intake opening 59 and pressure hose 57. This
pressure, at low speeds, is insufficient to overcome the force of the
compressed spring, so the slide valve 50 remains biased to its open
position, shown by solid lines in FIGS. 1 and 2. When slide valve 50 is in
its fully open position, the area of the water intake opening 20 is at its
maximum, enabling a large amount of water to enter the intake opening 20
without significant resistance.
As the rotational speed of impeller 38 is increased during acceleration of
the boat, the strength of the jet flow it produces will also increase. At
the beginning of acceleration, the rotational speed of impeller 38 is not
significantly increased, therefore the water pressure does not build up
sufficiently high in the constricted area 46 to overcome the force of the
compressed spring. Thus the slide valve 50 remains in its fully open
position.
Increased rotation of impeller 38 during acceleration further increases the
pressure in the constricted area 46, but it is still not great enough to
overcome the biasing force of the compressed spring. Accordingly, slide
valve 50 remains open.
When a high cruising speed is achieved, a dynamic pressure resulting from
the boat speed acts on the water intake opening. As a result, more water
enters water duct 40 and, with this increased water volume, the pressure
within constricted portion 46 increases further. This increased pressure
is transmitted to cylinder 54 by means of the pressure outlet 59 and
pressure hose 57. At this point, this pressure overcomes the force of the
compressed spring, thereby urging the piston rod toward the left (as seen
in FIG. 2) closing the slide valve 50. Closing slide valve 50 diminishes
the area of the water intake opening 20 so as to prevent more water from
entering the duct 40 than is needed. This prevents an increase in water
resistance at the water intake opening which would be present had the
water intake area not been reduced.
The second embodiment of the invention will be described with reference to
FIGS. 3-6. In this embodiment, elements having the same function as those
in the previously described embodiment are referred by the same reference
numerals increased by 100. It is to be understood that the impeller, water
duct and exit nozzle function in the same manner as in the previously
described embodiment.
As can be seen in FIG. 3, secondary water intake openings 162a and 162b are
located on either side of primary water intake 120, which is located in
the center of the boat bottom 112. Secondary water intake openings 162a
and 162b communicate with the inlet portion 142 of water duct 140 via
secondary ducts 160a and 160b and openings 163a and 163b. In this
embodiment, the primary water intake opening 120 does not have a slide
valve. Instead, slide valves 150a and 150b are operatively associated with
the secondary water intake openings 162a and 162b. Slide valves 150a and
150b do not partially open or close the secondary water intake openings
162a and 162b, but, rather, they can fully open or fully close these
openings to allow or prevent water from entering the secondary ducts 160a
and 160b.
The slide valves 150a and 150b may be operated by a motor 170, which may be
a DC motor, which is supported by the bottom 112 of the boat 110. Motor
170 has connecting rods 156a and 156b linking it to the slide valves 150a
and 150b, respectively, such that, when motor 170 operates, the slide
valves 150a and 150b can be opened or closed.
The jet pump system shown in FIGS. 3 and 4 utilizes a boat speed measuring
means to detect the speed of the boat and open or close the slide valves
150a and 150b in accordance with the boat speed. A control system, which
is schematically illustrated in FIGS. 5 and 6, has a power source 171,
means for measuring the boat speed 172, control circuit 173 and a drive
circuit 174. The boat speed measuring means 172 measures the speed of the
boat V. The control circuit 173 compares the measured boat speed V with a
predetermined speed .gamma. as illustrated in FIG. 6 and, if V is greater
than .gamma. a command signal is sent to motor drive circuit 174 and slide
valves 150a and 150b are closed. If V is less than or equal to .gamma.,
(during low speed operation), the drive signal to the motor 170b causes
the slide valves 150a and 150b to open.
During low speed operation and accelerating from low speed operation, the
secondary water intake openings 162a and 162b remain open to enable water
to enter through secondary ducts 160a and 160b into the water duct 140.
This insures a sufficient water supply to the impeller 138.
When high speed cruising has been attained, such that the V is greater than
.gamma., motor 170 closes the slide valves 150a and 150b so that water
cannot enter the secondary ducts 160a and 160b. Thus, water is drawn into
the water duct 140 only through the water intake opening 120.
In this embodiment, a sufficiently large area of water intake openings is
maintained during low speed operations so that sufficient water can be
drawn in when the dynamic pressure is insufficient. This allows good
acceleration characteristics. During high speed cruising operations, the
secondary water intake openings 162a and 162b are closed, leaving only
water intake opening 120 open so that the total water intake area
decreases to avoid undue resistance.
A third embodiment of the present invention will be described in reference
to FIGS. 7-9. In these figures, elements having the same functions as
those of the first embodiment will be referred to by the same numerals
increased by 200. It is to be understood that the water duct 242, 244 and
246, impeller 238 and exit nozzle 232 function the same as in the
previously described embodiments.
In this embodiment, a slide valve is not used, but a movable wall portion
280 is utilized to adjust the water entry angle of the forward section 242
of the water inlet duct. The movable wall 280 may be formed from a
flexible material, such as rubber, and may be located in an upstream wall
242a of the forward section 242. A leading edge of the movable wall 280 is
held in place between the front edge of the water intake opening 220 and
the screen 222. A trailing edge of the movable wall 280 is attached to the
upstream wall 242a of the forward section 242 such that it is flush
therewith.
A motor 270, which may be DC motor, is attached to an external side of the
upstream wall 242a. An arm member 273 is also pivotally attached to an
external side of the upstream wall 242a via pivot pin 274. A portion of
arm member 273 is formed as a sector gear which engages a worm gear 271
driven by the motor 270. A second, sliding arm 275 has one end pivotally
attached to the arm member 273 by pivot pin 278, while its opposite end is
linked to a pin 276 extending through an elongated hole formed in the
sliding arm 275. Pin 276 may be affixed to the upstream wall portion 242a.
The pivot pin 278 interconnects the arm member 273 and sliding arm 275.
The arm member 273 and sliding arm 275 are located such that they bear
against a side of the movable wall 280.
During low speed operations, the movable wall is positioned as shown in
FIG. 8. In this position, the movable wall 280 forms an angle .alpha. with
the bottom 112 of the boat. In order to change the water inlet angle of
movable wall 280 a drive command is issued to motor 270 which causes worm
gear 271 to rotate. Such rotation of worm gear 271 causes arm member 273
to rotate around pivot pin 274 in a clockwise direction (as shown in FIG.
8). Sliding arm 275 also slides around pin 276 in a counter clockwise
direction due to its connection with the arm 273 through pivot pin 278.
Such movement, as illustrated in FIG. 9, allows the movable wall 280 to
assume an angle .beta. with respect to the bottom of the boat. As can be
seen, angle .beta. is less than angle .alpha..
The movable wall 280 is positioned as shown in FIG. 8 during low speed
operations such that entry angle .alpha. is formed. This allows more water
to enter the water duct during low speed operations. When a transition is
made from low to high speed operations, the water entry angle is adjusted
to the smaller angle .beta. to lower the resistance during such operations
and to reduce the shear which occurs when too much water strikes the
upstream wall 242a. This retains the efficiency of the water intake
opening during high speed operations.
The drive command to motor 270 may be issued by a control system which
senses the boat speed similar to the control system illustrated in FIGS. 5
and 6.
Although, in this embodiment, the movable wall was illustrated as being
associated with an upstream wall portion of the water intake duct, it is
to be understood that a downstream wall 242b of duct could accommodate the
movable wall portion so as to vary the water entry angle.
The foregoing description is provided for illustrative purposes only and
should not be construed as in any way limiting this invention, the scope
of which is defined solely by the appended claims.
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